Depression and
Mood Changes
Certain infection(s) can trigger an autoimmune attack on the brain, resulting in inflammation and the onset of neuropsychiatric symptoms, including major depression, bipolar disorder and sudden mood changes.

Depression and Mood Changes
It would not be unusual for a person to be depressed or have sudden mood changes when confronted with a stressful or upsetting situation. But when it occurs frequently or continues for an extended period of time, it may signal a deeper problem.
New research indicates that infection(s) and immune dysfunction can play a role in triggering sudden changes in mood and behavior. Infection, immune dysfunction and neuroinflammation have all been implicated in chronic mental disorders such as major depressive disorder, anxiety, schizophrenia 1 and bipolar disorder. 2

Infections can trigger sudden mood changes

Mood disorders, including major depression and bipolar disorder (also known as manic depression) encompass a wide range of symptoms that can present differently in children, adolescents and adults.

For instance, a child who has depression may be irritable, hypercritical (i.e. negative thinking, complaining a lot) or appear sad or angry. While depressive disorders are characterized by depression, people with bipolar disorders tend to experience sudden mood changes, fluctuating between states of acute depression and euphoria or mania. 2

Mood disorders can be caused by a variety of factors including genetics, brain chemical imbalances, life stressors, and medical conditions, such as ADHD, thyroid disease, and dementia.

New research also indicates that infection(s) and immune dysfunction can play a role in triggering sudden changes in mood and personality. Infection, immune dysfunction and neuroinflammation have all been implicated in chronic mental disorders such as major depressive disorder, bipolar disorder, anxiety and schizophrenia.

In fact, researchers suspect that “a significant number of people believed to have schizophrenia or bipolar disorder actually have an immune system disorder that affects the brain’s receptors.” 3

A nationwide study found that people treated for a severe infection were 62% more likely to have developed a mood disorder than those who never had one. And multiple infections or the combination of a severe infection and having an autoimmune disease “boosted the odds of developing depression, bipolar disorder, or another mood disorder even further.” 4

Immune system attacks the brain

When an infection (bacterial, viral, fungal, parasitic) invades the body, the immune system produces antibodies to destroy the harmful foreign invader. But in some people, their immune response over reacts and their antibodies also mistakenly attack healthy cells in the brain.

This attack can trigger brain inflammation and the onset of psychiatric symptoms, including sudden mood and personality changes. When this occurs, the person may have an infection-triggered autoimmune encephalopathy. Unfortunately, patients with this condition may be misdiagnosed with bipolar disorder, chronic depression or other psychiatric illnesses.

Common infections can cause autoimmune attacks

Common infections can trigger an autoimmune attack. For instance, strep infections can trigger sudden mood changes in children and adolescents with Pediatric Autoimmune Neuropsychiatric Disorder Associated with Streptococcal infection (PANDAS) .

PANDAS patients can exhibit extreme emotional lability or mood changes, rages, anger outbursts, severe anxiety (including separation anxiety) as well as depression. They are frequently misdiagnosed as having a psychiatric illness, when, in fact, they may have a treatable autoimmune condition.

Strep, however, isn’t the only culprit. Other bacteria and viruses can trigger mood changes. In both children and adults, the herpes simplex virus, varicella zoster, Epstein-Barr virus, and possibly toxoplasmosis have been associated with depression. 5

And studies have found that people with chronic sinusitis may be more likely to have depression and anxiety. 6 Even a Borrelia burgdorferi infection (which causes Lyme disease) and a Bartonella henselae infection (which causes cat scratch disease) can trigger the onset of psychiatric symptoms, including major depression with psychotic features. 7 Additionally, coronaviruses, which typically affect the respiratory tract, and influenza have been associated with mood disorders. 8

  1. Lurie DI. An Integrative Approach to Neuroinflammation in Psychiatric disorders and Neuropathic Pain. J Exp Neurosci. 2018;12:1179069518793639. Published 2018 Aug 13. doi:10.1177/1179069518793639 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6090491/
  2. Benedetti F, Aggio V, Pratesi ML, Greco G, Furlan R. Neuroinflammation in Bipolar Depression. Front Psychiatry. 2020;11:71. Published 2020 Feb 26. doi:10.3389/fpsyt.2020.00071 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7054443/
  3. Rosenblat JD, McIntyre RS. Bipolar Disorder and Immune Dysfunction: Epidemiological Findings, Proposed Pathophysiology and Clinical Implications. Brain Sci. 2017;7(11):144. Published 2017 Oct 30. doi:10.3390/brainsci7110144
  4. Benros ME, Waltoft BL, Nordentoft M, et al. Autoimmune Diseases and Severe Infections as Risk Factors for Mood Disorders: A Nationwide Study. JAMA Psychiatry. 2013;70(8):812–820. doi:10.1001/jamapsychiatry.2013.1111
  5. Levin A. Researchers Consider Infection as One Cause of Depression. Psychiatric News. March 20, 2015. doi.org/10.1176/appi.pn.2015.3b14
  6. Kim J, Ko I, Kim MS, Yu MS, Cho B, Kim D. Association of Chronic Rhinosinusitis With Depression and Anxiety in a Nationwide Insurance Population. JAMA Otolaryngol Head Neck Surg. Published online February 07, 2019145(4):313–319. doi:10.1001/jamaoto.2018.4103
  7. Breitschwerdt, E. B., Greenberg, R., Maggi, R. G., Mozayeni, B. R., Lewis, A., & Bradley, J. M. (2019). Bartonella henselae Bloodstream Infection in a Boy With Pediatric Acute-Onset Neuropsychiatric Syndrome. Journal of Central Nervous System Disease. doi.org/10.1177/1179573519832014
  8. Okusaga O, Yolken RH, Langenberg P, et al. Association of seropositivity for influenza and coronaviruses with history of mood disorders and suicide attempts. J Affect Disord. 2011;130(1-2):220–225. doi:10.1016/j.jad.2010.09.029
Sudden Mood Changes

“Infections may be the driving force behind some mental health disorders including major depression and bipolar disorder.” 1

Recognizing autoimmune-induced neuropsychiatric symptoms like depression and sudden mood changes
How can an infection cause sudden mood changes?

Learn more about how infections can trigger neuropsychiatric symptoms

Cunningham Panel helps identify an autoimmune disorder in child initially diagnosed with schizophrenia

Cunningham Panel™ helps identify an autoimmune disorder in child initially diagnosed with schizophrenia

Researchers describe a complex case involving a 15-year-old girl, who abruptly developed multiple neurologic and psychiatric symptoms.

Autoimmune diseases and severe infections as risk factors for mood disorders: a nationwide study

Autoimmune diseases and severe infections as risk factors for mood disorders: a nationwide study

This nationwide, population-based, prospective cohort study examines the link between mood disorders, infections, and autoimmune disease.

Childhood infections can increase risk of mental illness in kids

Childhood infections can increase risk of mental illness in kids

Nationwide study finds both mild and severe infections can increase risk of mental disorders in children and adolescents.

  • Test Order Process
    The Cunningham Panel™ – Antibody testing that helps determine whether an autoimmune response may be triggering neurologic and/or psychiatric symptoms. 

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